Photon Avalanche Diode and Methods of Producing Thereof

ABSTRACT

A photon avalanche diode includes a semiconductor body having a first side and a second side opposite the first side, a primary doped region of a first conductivity type at the first side of the semiconductor body, a primary doped region of a second conductivity type opposite the first conductivity type at the second side of the semiconductor body, an enhancement region of the second conductivity type below and adjoining the primary doped region of the first conductivity type, the enhancement region forming an active pn-junction with the primary doped region of the first conductivity type, and a collection region of the first conductivity type interposed between the enhancement region and the primary doped region of the second conductivity type and configured to transport a photocarrier generated in the collection region or the primary doped region of the second conductivity type towards the enhancement region.

BACKGROUND

Single-photon avalanche diodes (SPADs) have high light detectionsensitivity and gain, and allow very fast read-out. SPADs may bearranged in an array to form a silicon photo-multiplier and are used inapplications such as LiDAR (light detection and ranging), proximitydetection sensors, time-of-flight (ToF) cameras, scintillator read-outsuch as in positron emission tomography (PET), time-resolvedluminescence read-out, gas sensing, bio molecule sensing, etc.

However, photon detection efficiency in the near infrared wavelengthspectrum is poor for SPAD sensors fabricated in Si technology. Si has alarge absorption depth at such wavelengths. As such, Si-based SPADs aretypically used in green short wavelength range applications rarely atnear infrared wavelength applications such as LiDAR at 905 nm, ToF at850 nm or 940 nm, etc.

Another limitation for SPADs is compactness. A larger SPAD pitch (size)results in less dynamic range (larger dead-time and higher dark countrate) and lower spatial resolution. However, SPADs typically operate athigh voltages which require an edge termination structure for properisolation. Reducing the sensor size down to a pitch of about 5 μm orless results in significant loss in SPAD photon detection efficiency dueto edge termination effects. A larger SPAD pitch (size) results in lesssensitivity.

Thus, there is a need for an improved SPAD cell design and relatedmethods of manufacture.

SUMMARY

According to an embodiment of a photon avalanche diode, the photonavalanche diode comprises: a semiconductor body having a first side anda second side opposite the first side; a primary doped region of a firstconductivity type at the first side of the semiconductor body; a primarydoped region of a second conductivity type opposite the firstconductivity type at the second side of the semiconductor body; anenhancement region of the second conductivity type below and adjoiningthe primary doped region of the first conductivity type, the enhancementregion forming an active pn-junction with the primary doped region ofthe first conductivity type; and a collection region of the firstconductivity type interposed between the enhancement region and theprimary doped region of the second conductivity type, and configured totransport a photocarrier generated in the collection region or theprimary doped region of the second conductivity type towards theenhancement region.

According to another embodiment of a photon avalanche diode, the photonavalanche diode comprises: a semiconductor body; a first diode, a seconddiode and a third diode formed in the semiconductor body, the seconddiode being a photodiode; a main cathode terminal connected to thecathode of the first diode; a main anode terminal connected to the anodeof the third diode; an auxiliary cathode terminal connected to thecathode of the third diode and to the cathode of the second diode; andan auxiliary anode terminal connected to the anode of the first diodeand to the anode of the second diode, wherein the main anode terminal iselectrically connected to ground or a reference potential, wherein themain cathode terminal is electrically connected to a voltage whichcauses a photocarrier multiplication region to form within thesemiconductor body, wherein the auxiliary anode terminal is electricallyconnected to ground or to a read-out circuit, wherein the auxiliarycathode terminal is electrically connected to a constant bias voltageless than a voltage applied to the main cathode terminal.

According to an embodiment of a method of producing a photon avalanchediode, the method comprises: forming a primary doped region of a firstconductivity type at a first side of a semiconductor body; forming aprimary doped region of a second conductivity type opposite the firstconductivity type at a second side of the semiconductor body oppositethe first side; forming an enhancement region of the second conductivitytype below and adjoining the primary doped region of the firstconductivity type, the enhancement region forming an active pn-junctionwith the primary doped region of the first conductivity type; andforming a collection region of the first conductivity type interposedbetween the enhancement region and the primary doped region of thesecond conductivity type, and configured to transport a photocarriergenerated in the collection region or the primary doped region of thesecond conductivity type towards the enhancement region.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description, and uponviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

The elements of the drawings are not necessarily to scale relative toeach other. Like reference numerals designate corresponding similarparts. The features of the various illustrated embodiments can becombined unless they exclude each other. Embodiments are depicted in thedrawings and are detailed in the description which follows.

FIG. 1A illustrates a partial cross-sectional view of an embodiment of asingle-photon avalanche diode (SPAD).

FIG. 1B illustrates an electric field potential distribution within partof the SPAD shown in FIG. 1A.

FIG. 2A illustrates a partial plan view of another embodiment of a SPAD.

FIG. 2B illustrates a partial cross-sectional view of the SPAD in FIG.2A, along the line labelled A-A′.

FIG. 3 illustrates a circuit schematic of the SPADs illustrated in FIGS.1 and 2A-2B with a read-out circuit.

FIGS. 4 through 7 illustrate respective circuit schematics of differentembodiments of the read-out circuit shown in FIG. 3.

FIGS. 8A and 8B illustrate partial cross-sectional views of anembodiment of producing the SPAD shown in FIGS. 2A and 2B.

DETAILED DESCRIPTION

The embodiments described provide a single-photon avalanche diode (SPAD)having a collection region where photocarriers such as photoelectrons orphotoholes are collected and directed to the multiplication region ofthe SPAD. The multiplication region, which is above the collectionregion and formed between one of the primary (cathode or anode) dopedregions of the device and an enhancement region of the oppositeconductivity type, includes a breakdown mechanism which causesmultiplication to occur. The collection region directs photocarriersgenerated deeper in the SPAD structure upward toward the multiplicationregion, improving efficiency for longer wavelength light.

The SPAD may also include an auxiliary (virtual) doped region of thesame conductivity type as the enhancement region and which forms acounter electrode to the primary doped region of the SPAD adjoining theenhancement region. The auxiliary doped region of the same conductivitytype as the enhancement region is electrically isolated from the primarydoped region of the SPAD adjoining the enhancement region, e.g., by anauxiliary doped region of the opposite conductivity type as theenhancement region and which is biased differently than the primarydoped region adjoining the enhancement region. The potential of theauxiliary doped region of the same conductivity type as the enhancementregion is not necessarily fixed. For example, the auxiliary doped regionof the same conductivity type as the enhancement region may have avariable electric potential and be used as a readout terminal/electrode.

Described next in more detail are various embodiments of the SPAD celldesign and methods of manufacturing the SPAD. In this context, theprimary cathode region is shown at one side of the SPAD, the primaryanode region at the opposite side of the SPAD, the enhancement regionadjoining the primary cathode region, and the collection regionseparating the enhancement region and the primary cathode region fromthe primary anode region. However, the position of the primary cathodeand primary anode regions may be switched/reversed. That is, theenhancement region may instead adjoin the primary anode region at oneside of the SPAD, and the collection region may instead separate theenhancement region and the primary anode region from the primary cathoderegion. Accordingly, the phrase “a primary doped region of a firstconductivity type” may refer to either the primary cathode region or theprimary anode region, depending on the position of the primary cathodeand anode regions, and the phrase “a primary doped region of a secondconductivity type” refers to the other primary doped region of thedevice (anode/cathode).

FIG. 1A illustrates a partial cross-sectional view of an embodiment of aSPAD 100. The SPAD 100 includes a semiconductor body 102 having a firstside 104 and a second side 106 opposite the first side 104. A primarycathode (C) region 108 of a first conductivity type is formed at thefirst side 104 of the semiconductor body 102. A primary anode (A) region110 of a second conductivity type opposite the first conductivity typeis formed at the second side 106 of the semiconductor body 102. In oneembodiment, the semiconductor body 102 is a Si body, the firstconductivity type is n-type, and the second conductivity type is p-type.The Si body 102 may include a base Si substrate and one or moreepitaxial layers grown on the base Si substrate. Other types ofsemiconductor material may be used for the semiconductor body 102.

An enhancement region 112 of the second conductivity type (e.g. p-type)is formed below and adjoining the primary cathode region 108. Acollection region 114 of the first conductivity type (e.g. n-type) isinterposed between the enhancement region 112 and the primary anoderegion 110.

The collection region 114 is more weakly doped than the primary cathoderegion 108, the primary anode region 110, and the enhancement region112. The collection region 114 is configured to transport a photocarriergenerated in the collection region 114 or the primary anode region 110towards the enhancement region 112. The photocarrier is a photoelectronin the case of an n-type collection region 114 and a photohole in thecase of a p-type collection region 114. The enhancement region 112 formsan active pn-junction with the primary cathode region 108. FIG. 1Aincludes an enlarged view of part of the SPAD 100 that includes theprimary cathode region 108, the enhancement region 112 and thecollection region 114.

The SPAD 100 may also include an auxiliary anode (A_(v)) region 116 ofthe second conductivity type at the first side 104 of the semiconductorbody 102. The auxiliary anode region 116 is also referred to herein as avirtual anode region because the SPAD 100 already includes the primaryanode region 110 at the second side 106 of the semiconductor body 102and which is typically connected to ground. The auxiliary anode region116 is more heavily doped than the enhancement region 112 and laterallyspaced apart from the primary cathode region 108. For example, the SPAD100 may include a dielectric isolation 118 such as a shallow trenchisolation (STI) structure laterally interposed between the primarycathode region 108 and the auxiliary anode region 116 at the first side104 of the semiconductor body 102. According to this example, theenhancement region 112 may laterally extend to the auxiliary anoderegion 116 and the doping concentration of the enhancement region 112may decrease in a region 112′ of the enhancement region 112 which isadjacent to where the dielectric isolation 118 meets the primary cathoderegion 108, to prevent a high electric field near the dielectricisolation 118. That is, the primary cathode region 108 of the firstconductivity type may stop at the edge of the dielectric isolation 118and the dielectric isolation 118 may adjoin a relatively weakly dopedregion 112′ of the second conductivity type. The primary cathode region108 may include a highly doped surface region 120 to prevent depletionat the first side 104 of the semiconductor body 102.

Further according to the embodiment illustrated in FIG. 1A, theauxiliary anode region 116 is vertically separated from the primaryanode region 110 by the collection region 114. The auxiliary anoderegion 116, if provided, may have a variable electric potential and beused as a readout terminal/electrode as described in more detail laterherein. The auxiliary anode region 116 instead may be omitted.

During operation of the SPAD 100, the primary cathode region 108 isbiased at a voltage, e.g., about 20V and which results in a highelectric field between the primary cathode region 108 and theenhancement region 112 of the opposite conductivity type. This highelectric field defines a multiplication region between the primarycathode region 108 and the enhancement region 112 and which isconfigured to cause avalanche multiplication when a single electronenters the high field multiplication region. This is commonly referredto as Geiger mode of operation. The biasing of the primary cathoderegion 108 also causes full depletion of the enhancement region 112, viathe multiplication region, so that an attractive potential is createdfor electrons located in the underlying collection region 114.

A photon absorbed in the collection region 114 or in the underlyingprimary anode region 110 creates an electron-hole pair, wherein theelectron is also referred to herein as photoelectron and the hole asphotohole. In the case of an n-type collection region 114, aphotoelectron is transported by the collection region 114 towards themultiplication region and initiates avalanche breakdown, whereas thephotohole is transported to the primary anode region 110. Avalancheelectrons and avalanche holes are created in the multiplication regionwhen avalanche breakdown occurs, rapidly discharging the junctioncapacitance between the primary cathode region 108 and the enhancementregion 112. Due to the applied voltages of the SPAD 100, the avalancheelectrons are transported to the primary cathode region 108 and theavalanche holes are transported to the (virtual) auxiliary anode region116, if provided, and which results in a current flowing through anexternal supply network (not shown in FIG. 1A). In the case of an p-typecollection region 114, a photohole is instead transported by thecollection region 114 towards the multiplication region to initiateavalanche breakdown.

The resulting current causes a voltage drop over a quenching resistor Rq(not shown in FIG. 1A), reducing the voltage drop between the primarycathode region 108 and the primary anode region 110, or the auxiliaryanode 116, if provided, and thus quenching the avalanche process. Thejunction capacitance is then recharged to the initial condition throughthe quenching resistor, to enable a subsequent avalanche process. Thequenching resistor may be located at the cathode side of the SPAD 100 orthe (virtual) auxiliary anode side, if provided. Also, active devicesmay be used to control the quenching and recharging process, asdescribed in more detail later herein.

The signal is also visible at the auxiliary anode region 116, ifprovided, because recharging of the junction capacitance takes place bya current flowing from the primary cathode region 108 to the auxiliaryanode region 116. Accordingly, the current can be seen at the auxiliaryanode region 116. The signal present at the auxiliary anode region 116can be read out at a relatively small voltage and therefore high-voltagecircuitry is not needed to read the signal. The current flowing into theauxiliary anode region 116 may be detected, for example, by acharge-integrating circuit or a transimpedance amplifier. The potentialvariation present at the auxiliary anode region 116 may be used todirectly control, e.g., CMOS gates to create a digital output pulsesignal.

If the auxiliary anode region 116 is included in the SPAD 100, the SPAD100 may also include an auxiliary cathode (C_(b)) region 122 of thefirst conductivity type at the first side 104 of the semiconductor body102. The auxiliary anode region 116 is laterally interposed between theauxiliary cathode region 122 and the primary cathode region 108 at thefirst side 104 of the semiconductor body 102, e.g., as shown in FIG. 1A.

The auxiliary cathode region 122 is connected to the collection region114 at the edge of the SPAD cell, establishing an extra depletion zoneand providing the electric field potential distribution shown in FIG.1B. The auxiliary cathode region 122 also isolates the auxiliary anoderegion 116 from the primary anode region 110 of the SPAD 100. Forexample, the auxiliary anode region 116 may be electrically connected toground or to a read-out circuit (not shown in FIG. 1A). The auxiliarycathode region 122 may be electrically connected to a constant biasvoltage, e.g., in the single volt range and which depletes thecollection region 114 such that the auxiliary anode region 116 iselectrically isolated from the primary anode region 110. For example,the auxiliary cathode region 122 may be electrically connected to afixed voltage such as the supply voltage of a CMOS chip.

The SPAD 100 may also include columnar regions 124 of the secondconductivity type and which vertically extend from the primary anoderegion 110 and laterally confine the collection region 114 below theenhancement region 112. The auxiliary anode region 116, if provided, iselectrically isolated from the columnar regions 124 of the secondconductivity type by the collection region 114 in FIG. 1A. The columnarregions 124 of the second conductivity type impart curvature toequipotential lines within the SPAD 100, based on the work functiondifference between n-type and p-type semiconductor material and thedoping concentration in the columnar regions 124. The columnar regions124 of the second conductivity type thus aid in directing photoelectronsor photoholes (depending on the conductivity types) toward the center ofthe SPAD 100, allowing for a smaller multiplication region. The edgetermination region, which may be the region laterally extending outsidethe multiplication region, may remain the same size whereas themultiplication region may be made smaller and therefore provide asmaller SPAD cell pitch. In one embodiment, the auxiliary anode region116 and the auxiliary cathode region 122 are part of the edgetermination.

As explained above, the position of the primary cathode and primaryanode regions 108, 110 of the SPAD 100 in FIGS. 1A-1B may beswitched/reversed so that the primary cathode region 108 is disposed atthe second side 106 of the semiconductor body 102 and the primary anoderegion 110 is disposed at the first side 104 of the semiconductor body102. The position of the enhancement region 112, the collection region114, the auxiliary anode region 116, and the auxiliary cathode region122 remain the same in either configuration (primary cathode region 108at the first side 104 and primary anode region 110 at the second side106, or primary anode region 110 at the first side 104 and primarycathode region 108 at the second side 106). The auxiliary anode region116 is also referred to herein as auxiliary doped region of the secondconductivity type. The auxiliary cathode region 122 is also referred toherein as auxiliary doped region of the first conductivity type.

FIGS. 2A and 2B illustrate another embodiment of a SPAD 200. FIG. 2A isa partial plan view of the SPAD 200, and FIG. 2B is a partialcross-sectional view of the SPAD 200. The cross-section of FIG. 2B istaken along the line labelled A-A′ in FIG. 2A. The SPAD 200 may have aconcentric layout as shown in FIG. 2A, in that the primary cathoderegion 108 is laterally surrounded by the auxiliary anode region 116which in turn is laterally surrounded by the auxiliary cathode region122 in a series of concentric ring-like structures. However, this isjust one example. The SPAD 200 may instead have a different layout.

The embodiment illustrated in FIGS. 2A and 2B is similar to theembodiment illustrated in FIG. 1A. Different, however, the columnarregions 124 of the second conductivity type shown in FIG. 1A are omittedfrom the SPAD 200 shown in FIGS. 2A and 2B. Also in FIGS. 2A and 2B, thecollection region 114 laterally separates the primary cathode region 108from the auxiliary anode region 116, if provided, at the first side 104of the semiconductor body 102. According to this embodiment, theenhancement region 112 does not laterally extend to the auxiliary anoderegion 116. Instead, the collection region 114 laterally separates theenhancement region 112 from the auxiliary anode region 116 in thisembodiment.

As explained above, the position of the primary cathode and primaryanode regions 108, 110 of the SPAD 200 in FIGS. 2A-2B may beswitched/reversed so that the primary cathode region 108 is disposed atthe second side 106 of the semiconductor body 102 and the primary anoderegion 110 is disposed at the first side 104 of the semiconductor body102. The position of the enhancement region 112, the collection region114, the auxiliary anode region 116, and the auxiliary cathode region122 remain the same in either configuration (primary cathode region 108at the first side 104 and primary anode region 110 at the second side106, or primary anode region 110 at the first side 104 and primarycathode region 108 at the second side 106).

FIG. 3 illustrates a circuit schematic of the SPADs 100, 200 illustratedin FIGS. 1 and 2A-2B. Each SPAD 100, 200 includes a first diode D1, asecond diode D2 and a third diode D3 formed in a semiconductor body 102which is schematically illustrated in FIG. 3. The second diode D2 is aphotodiode. The first diode D1 and the third diode D3 may be p-njunction diodes, respectively.

Each SPAD 100, 200 also includes a main cathode terminal C connected tothe cathode C1 of the first diode D1, a main anode terminal A connectedto the anode A3 of the third diode D3, an auxiliary cathode terminalC_(b) connected to the cathode C3 of the third diode D3 and to thecathode C2 of the second diode D2, and an auxiliary anode terminal A_(v)connected to the anode A1 of the first diode D1 and to the anode A2 ofthe second diode D2. The main anode terminal A is electrically connectedto ground or a reference potential. The main cathode terminal C iselectrically connected to a voltage which causes a photoelectronmultiplication region to form within the semiconductor body 102. Theauxiliary anode terminal A_(v) is electrically connected to ground or toa read-out circuit. The auxiliary cathode terminal C_(b) is electricallyconnected to a constant bias voltage less than the voltage applied tothe main cathode terminal C.

Under these biasing conditions, a photoelectron initiates avalanchebreakdown within a multiplication region of the SPAD 100, 200. Theresulting avalanche electrons are transported to the main cathodeterminal C and the resulting avalanche holes are transported to theauxiliary anode terminal A_(v). A read-out circuit 300 may beelectrically connected to the auxiliary anode terminal A_(v), theread-out circuit 300 being configured to detect current flowing from theprimary cathode region 108 to the auxiliary anode region 110 of the SPAD100, 200 during recharging of the junction capacitance between theenhancement region 112 and the primary cathode region 108 after anavalanche event. The read-out circuit 300 may be integrated in the samedie (chip) as the SPAD 100, 200 or may be formed in a separate die.Described next are various embodiments of the read-out circuit 300.

FIG. 4 illustrates an embodiment of the read-out circuit 300. Accordingto this embodiment, passive quenching is applied to the primary cathoderegion 108 of the SPAD 100, 200 via a quenching resistor R_(q) connectedbetween the main cathode terminal C of the SPAD 100, 200 and a voltagesupply V_(CC) for biasing the primary cathode region 108. A lower biasvoltage VDD is applied to the auxiliary cathode terminal C_(b) of theSPAD 100, 200 for biasing the auxiliary cathode region 122 of the SPAD100, 200. The read-out circuit 300 is a charge-integrating circuit inFIG. 4, where the charge-integrating circuit includes an operationalamplifier 400 and a capacitor Ci coupled across the negative inputterminal and the output terminal of the operational amplifier 400. Thecharge-integrating circuit converts a current pulse that emerges at theauxiliary anode terminal A_(v) of the SPAD 100, 200 to a voltage V_(out)which can be read out. The charge-integrating circuit instead may beimplemented as a transimpedance amplifier, e.g., by replacing capacitorC_(i) with a resistor.

FIG. 5 illustrates another embodiment of the read-out circuit 300. Theembodiment shown in FIG. 5 is similar to the embodiment shown in FIG. 4in that passive quenching is applied to the primary cathode region 108of the SPAD 100, 200 via a quenching resistor R_(q) connected betweenthe main cathode terminal C of the SPAD 100, 200 and voltage supplyV_(CC). Different, however, the charge-integrating circuit of theread-out circuit 300 includes a current mirror 500 for mirroring acurrent pulse that emerges at the auxiliary anode terminal A_(v) of theSPAD 100, 200. A capacitor C_(s) is charged to a level which correspondsto the mirrored current. A readout circuit formed by transistors Q1, Q2senses the voltage across the capacitor C_(s) when a ‘select’ signal isactive. The sensed capacitor voltage may be sensed/detected by a columnamplifier similar to a memory cell readout operation, or may besensed/detected by another type of sensing circuit. The capacitor C_(s)is discharged by transistor Q3 responsive to a ‘reset’ signal.

FIG. 6 illustrates another embodiment of the read-out circuit 300.According to this embodiment, passive quenching is applied to theauxiliary anode region 116 of the SPAD 100, 200 via a quenching resistorR_(q) connected to the auxiliary anode terminal A_(v) of the SPAD 100,200. The read-out circuit 300 includes a pMOS device P1 coupled inseries with an nMOS device N1 to form a digital pulse output Vout whichcorresponds to a current pulse that emerges at the auxiliary anodeterminal A_(v) of the SPAD 100, 200.

FIG. 7 illustrates another embodiment of the read-out circuit 300.According to this embodiment, active quenching is applied to theauxiliary anode region 116 of the SPAD 100, 200. For example, a pMOSdevice P2 may provide active quenching when switched on by signal‘active quench’ and an nMOS device N2 may provide active recharging whenswitched on by signal ‘active recharge. The pMOS device P2 and the nMOSdevice N2 are coupled together at a common node which is also coupled tothe auxiliary anode terminal A_(v) of the SPAD 100, 200. The read-outcircuit 300 in FIG. 7 is the same as in FIG. 6, and provides a digitalpulse output Vout corresponding to a current pulse that emerges at theauxiliary anode terminal A_(v) of the SPAD 100, 200.

FIGS. 8A and 8B illustrate partial cross-sectional views of anembodiment of producing the SPAD 200 shown in FIGS. 2A and 2B.

In FIG. 8A, a first mask 800 with an opening 802 that defines theauxiliary anode region 116 of the SPAD 200 is formed on the first side104 of the semiconductor body 102. The opening 802 in the first mask 800partially overlaps with the dielectric isolation 118 by a distance ‘d1’so that an inward part 118′ of the dielectric isolation 118 remainscovered by the first mask 800. In one embodiment, the first mask 800 isa photoresist. Dopants 804 of the second conductivity type are thenimplanted into the first side 104 of the semiconductor body 102 throughthe opening 802 in the first mask 800 to form the auxiliary anode region116 of the SPAD 200. Implant energy, implant dose and parameters of asubsequent anneal determine the profile of the auxiliary anode region116.

In FIG. 8B, a second mask 806 having an opening 808 which has no overlapwith the dielectric isolation 118 is formed on the first side 104 of thesemiconductor body 102. Accordingly, the second mask 806 laterallyextends inward beyond an edge 810 of the dielectric isolation 118 by adistance ‘d2’. In one embodiment, the second mask 806 is a photoresist.Dopants 810 of the second conductivity type and dopants 812 of the firstconductivity type are then implanted into the first side 104 of thesemiconductor body 102 through the opening 808 in the second mask 806 toform the enhancement region 112 and the primary cathode region 108,respectively, of the SPAD 200. Implant energy, implant dose andparameters of a subsequent anneal determine the profile of theenhancement region 112 and the primary cathode region 108, respectively.

Although the present disclosure is not so limited, the followingnumbered examples demonstrate one or more aspects of the disclosure.

Example 1. A photon avalanche diode, comprising: a semiconductor bodyhaving a first side and a second side opposite the first side; a primarydoped region of a first conductivity type at the first side of thesemiconductor body; a primary doped region of a second conductivity typeopposite the first conductivity type at the second side of thesemiconductor body; an enhancement region of the second conductivitytype below and adjoining the primary doped region of the firstconductivity type, the enhancement region forming an active pn-junctionwith the primary doped region of the first conductivity type; and acollection region of the first conductivity type interposed between theenhancement region and the primary doped region of the secondconductivity type, and configured to transport a photocarrier generatedin the collection region or the primary doped region of the secondconductivity type towards the enhancement region.

Example 2. The photon avalanche diode of example 1, wherein thesemiconductor body is a Si body, wherein the first conductivity type isn-type, wherein the second conductivity type is p-type, wherein theprimary doped region of the first conductivity type is a primary cathoderegion of the photon avalanche diode, and wherein the primary dopedregion of the second conductivity type is a primary anode region of thephoton avalanche diode.

Example 3. The photon avalanche diode of examples 1 or 2, furthercomprising: an auxiliary doped region of the second conductivity type atthe first side of the semiconductor body and laterally spaced apart fromthe primary doped region of the first conductivity type, wherein theauxiliary doped region of the second conductivity type is verticallyseparated from the primary doped region of the second conductivity typeby the collection region.

Example 4. The photon avalanche diode of example 3, further comprising:an auxiliary doped region of the first conductivity type at the firstside of the semiconductor body, wherein the auxiliary doped region ofthe second conductivity type is laterally interposed between theauxiliary doped region of the first conductivity type and the primarydoped region of the first conductivity type at the first side of thesemiconductor body.

Example 5. The photon avalanche diode of example 4, wherein theauxiliary doped region of the second conductivity type is electricallyconnected to ground or to a read-out circuit, wherein the auxiliarydoped region of the first conductivity type is electrically connected toa constant bias voltage which depletes the collection region such thatthe auxiliary doped region of the second conductivity type iselectrically isolated from the primary doped region of the secondconductivity type, wherein the primary doped region of the firstconductivity type is electrically connected to a voltage which causes ahigh electric field multiplication region to form between the primarydoped region of the first conductivity type and the enhancement region,and wherein the multiplication region is configured to fully deplete theenhancement region and to enter avalanche multiplication when a singleelectron enters the multiplication region.

Example 6. The photon avalanche diode of any of examples 3 through 5,further comprising a read-out circuit electrically connected to theauxiliary doped region of the second conductivity type and configured todetect current flowing from the primary doped region of the firstconductivity type to the auxiliary doped region of the secondconductivity type during recharging of a junction capacitance betweenthe enhancement region and the primary doped region of the firstconductivity type after an avalanche event.

Example 7. The photon avalanche diode of example 6, wherein passivequenching is applied to the primary doped region of the firstconductivity type, and wherein the read-out circuit comprises acharge-integrating circuit or a transimpedance amplifier.

Example 8. The photon avalanche diode of example 6, wherein active orpassive quenching is applied to the auxiliary doped region of the secondconductivity type, and wherein the read-out circuit has a digital pulseoutput.

Example 9. The photon avalanche diode of any of examples 3 through 8,wherein the auxiliary doped region of the second conductivity type has avariable electric potential.

Example 10. The photon avalanche diode of any of examples 3 through 9,further comprising: columnar regions of the second conductivity type andwhich vertically extend from the primary doped region of the secondconductivity type and laterally confine the collection region below theenhancement region, wherein the auxiliary doped region of the secondconductivity type is electrically isolated from the columnar regions.

Example 11. The photon avalanche diode of any of examples 3 through 10,further comprising: dielectric isolation between the primary dopedregion of the first conductivity type and the auxiliary doped region ofthe second conductivity type at the first side of the semiconductorbody, wherein a doping concentration of the enhancement region decreasesin a region of the enhancement region which is adjacent to where thedielectric isolation meets the primary doped region of the firstconductivity type. The enhancement region may or may not laterallyextend to the auxiliary doped region of the second conductivity type inthis example.

Example 12. A photon avalanche diode, comprising: a semiconductor body;a first diode, a second diode and a third diode formed in thesemiconductor body, the second diode being a photodiode; a main cathodeterminal connected to the cathode of the first diode; a main anodeterminal connected to the anode of the third diode; an auxiliary cathodeterminal connected to the cathode of the third diode and to the cathodeof the second diode; and an auxiliary anode terminal connected to theanode of the first diode and to the anode of the second diode, whereinthe main anode terminal is electrically connected to ground or areference potential, wherein the main cathode terminal is electricallyconnected to a voltage which causes a photocarrier multiplication regionto form within the semiconductor body, wherein the auxiliary anodeterminal is electrically connected to ground or to a read-out circuit,wherein the auxiliary cathode terminal is electrically connected to aconstant bias voltage less than a voltage applied to the main cathodeterminal.

Example 13. The photon avalanche diode of example 12, further comprisinga read-out circuit electrically connected to the auxiliary anodeterminal.

Example 14. The photon avalanche diode of example 13, wherein passivequenching is applied to the main cathode terminal, and wherein theread-out circuit comprises a charge-integrating circuit or atransimpedance amplifier.

Example 15. The photon avalanche diode of example 13, wherein active orpassive quenching is applied to the auxiliary anode terminal, andwherein the read-out circuit has a digital pulse output.

Example 16. A method of producing a photon avalanche diode, the methodcomprising: forming a primary doped region of a first conductivity typeat a first side of a semiconductor body; forming a primary doped regionof a second conductivity type opposite the first conductivity type at asecond side of the semiconductor body opposite the first side; formingan enhancement region of the second conductivity type below andadjoining the primary doped region of the first conductivity type, theenhancement region forming an active pn-junction with the primary dopedregion of the first conductivity type; and forming a collection regionof the first conductivity type interposed between the enhancement regionand the primary doped region of the second conductivity type, andconfigured to transport a photocarrier generated in the collectionregion or the primary doped region of the second conductivity typetowards the enhancement region.

Example 17. The method of example 16, wherein the semiconductor body isa Si body, wherein the first conductivity type is n-type, wherein thesecond conductivity type is p-type, wherein the primary doped region ofthe first conductivity type is a primary cathode region of the photonavalanche diode, and wherein the primary doped region of the secondconductivity type is a primary anode region of the photon avalanchediode.

Example 18. The method of example 16 or 17, further comprising: formingan auxiliary doped region of the second conductivity type at the firstside of the semiconductor body and laterally spaced apart from theprimary doped region of the first conductivity type, wherein theauxiliary doped region of the second conductivity type is verticallyseparated from the primary doped region of the second conductivity typeby the collection region.

Example 19. The method of example 18, further comprising: forming anauxiliary doped region of the first conductivity type at the first sideof the semiconductor body, wherein the auxiliary doped region of thesecond conductivity type is laterally interposed between the auxiliarydoped region of the first conductivity type and the primary doped regionof the first conductivity type at the first side of the semiconductorbody.

Example 20. The method of example 18 or 19, further comprising: formingcolumnar regions of the second conductivity type and which verticallyextend from the primary doped region of the second conductivity type andlaterally confine the collection region below the enhancement region,wherein the auxiliary doped region of the second conductivity type iselectrically isolated from the columnar regions.

Example 21. The method of any of examples 18 through 20, furthercomprising: forming a dielectric isolation between the primary dopedregion of the first conductivity type and the auxiliary doped region ofthe second conductivity type at the first side of the semiconductorbody, wherein a doping concentration of the enhancement region decreasesin a region of the enhancement region which is adjacent to where thedielectric isolation meets the primary doped region of the firstconductivity type. The enhancement region may or may not laterallyextend to the auxiliary doped region of the second conductivity type inthis example.

Example 22. The method of example 21, wherein forming the auxiliarydoped region of the second conductivity type comprises: forming aphotoresist on the first side of the semiconductor body, the photoresisthaving an opening which partially overlaps with the dielectric isolationso that an inward part of the dielectric isolation remains covered bythe photoresist; and implanting dopants of the second conductivity typeinto the first side of the semiconductor body through the opening in thephotoresist.

Example 23. The method of examples 21 or 22, wherein forming the primarydoped region of the first conductivity type and the enhancement regioncomprises: forming a photoresist on the first side of the semiconductorbody, the photoresist having an opening which has no overlap with thedielectric isolation so that the photoresist laterally extends inwardbeyond an edge of the dielectric isolation; and implanting dopants ofthe second conductivity type and dopants of the first conductivity typeinto the first side of the semiconductor body through the opening in thephotoresist.

Terms such as “first”, “second”, and the like, are used to describevarious elements, regions, sections, etc. and are also not intended tobe limiting. Like terms refer to like elements throughout thedescription.

As used herein, the terms “having”, “containing”, “including”,“comprising” and the like are open ended terms that indicate thepresence of stated elements or features, but do not preclude additionalelements or features. The articles “a”, “an” and “the” are intended toinclude the plural as well as the singular, unless the context clearlyindicates otherwise.

It is to be understood that the features of the various embodimentsdescribed herein may be combined with each other, unless specificallynoted otherwise.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A photon avalanche diode, comprising: asemiconductor body having a first side and a second side opposite thefirst side; a primary doped region of a first conductivity type at thefirst side of the semiconductor body; a primary doped region of a secondconductivity type opposite the first conductivity type at the secondside of the semiconductor body; an enhancement region of the secondconductivity type below and adjoining the primary doped region of thefirst conductivity type, the enhancement region forming an activepn-junction with the primary doped region of the first conductivitytype; and a collection region of the first conductivity type interposedbetween the enhancement region and the primary doped region of thesecond conductivity type, and configured to transport a photocarriergenerated in the collection region or the primary doped region of thesecond conductivity type towards the enhancement region.
 2. The photonavalanche diode of claim 1, wherein the semiconductor body is a Si body,wherein the first conductivity type is n-type, wherein the secondconductivity type is p-type, wherein the primary doped region of thefirst conductivity type is a primary cathode region of the photonavalanche diode, and wherein the primary doped region of the secondconductivity type is a primary anode region of the photon avalanchediode.
 3. The photon avalanche diode of claim 1, further comprising: anauxiliary doped region of the second conductivity type at the first sideof the semiconductor body and laterally spaced apart from the primarydoped region of the first conductivity type, wherein the auxiliary dopedregion of the second conductivity type is vertically separated from theprimary doped region of the second conductivity type by the collectionregion.
 4. The photon avalanche diode of claim 3, further comprising: anauxiliary doped region of the first conductivity type at the first sideof the semiconductor body, wherein the auxiliary doped region of thesecond conductivity type is laterally interposed between the auxiliarydoped region of the first conductivity type and the primary doped regionof the first conductivity type at the first side of the semiconductorbody.
 5. The photon avalanche diode of claim 4, wherein the auxiliarydoped region of the second conductivity type is electrically connectedto ground or to a read-out circuit, wherein the auxiliary doped regionof the first conductivity type is electrically connected to a constantbias voltage which depletes the collection region such that theauxiliary doped region of the second conductivity type is electricallyisolated from the primary doped region of the second conductivity type,wherein the primary doped region of the first conductivity type iselectrically connected to a voltage which causes a high electric fieldmultiplication region to form between the primary doped region of thefirst conductivity type and the enhancement region, and wherein themultiplication region is configured to fully deplete the enhancementregion and to enter avalanche multiplication when a single electronenters the multiplication region.
 6. The photon avalanche diode of claim3, further comprising a read-out circuit electrically connected to theauxiliary doped region of the second conductivity type and configured todetect current flowing from the primary doped region of the firstconductivity type to the auxiliary doped region of the secondconductivity type during recharging of a junction capacitance betweenthe enhancement region and the primary doped region of the firstconductivity type after an avalanche event.
 7. The photon avalanchediode of claim 6, wherein passive quenching is applied to the primarydoped region of the first conductivity type, and wherein the read-outcircuit comprises a charge-integrating circuit or a transimpedanceamplifier.
 8. The photon avalanche diode of claim 6, wherein active orpassive quenching is applied to the auxiliary doped region of the secondconductivity type, and wherein the read-out circuit has a digital pulseoutput.
 9. The photon avalanche diode of claim 3, wherein the auxiliarydoped region of the second conductivity type has a variable electricpotential.
 10. The photon avalanche diode of claim 3, furthercomprising: columnar regions of the second conductivity type and whichvertically extend from the primary doped region of the secondconductivity type and laterally confine the collection region below theenhancement region, wherein the auxiliary doped region of the secondconductivity type is electrically isolated from the columnar regions.11. The photon avalanche diode of claim 3, further comprising:dielectric isolation between the primary doped region of the firstconductivity type and the auxiliary doped region of the secondconductivity type at the first side of the semiconductor body, wherein adoping concentration of the enhancement region decreases in a region ofthe enhancement region which is adjacent to where the dielectricisolation meets the primary doped region of the first conductivity type.12. A photon avalanche diode, comprising: a semiconductor body; a firstdiode, a second diode and a third diode formed in the semiconductorbody, the second diode being a photodiode; a main cathode terminalconnected to the cathode of the first diode; a main anode terminalconnected to the anode of the third diode; an auxiliary cathode terminalconnected to the cathode of the third diode and to the cathode of thesecond diode; and an auxiliary anode terminal connected to the anode ofthe first diode and to the anode of the second diode, wherein the mainanode terminal is electrically connected to ground or a referencepotential, wherein the main cathode terminal is electrically connectedto a voltage which causes a photocarrier multiplication region to formwithin the semiconductor body, wherein the auxiliary anode terminal iselectrically connected to ground or to a read-out circuit, wherein theauxiliary cathode terminal is electrically connected to a constant biasvoltage less than a voltage applied to the main cathode terminal. 13.The photon avalanche diode of claim 12, further comprising a read-outcircuit electrically connected to the auxiliary anode terminal.
 14. Thephoton avalanche diode of claim 13, wherein passive quenching is appliedto the main cathode terminal, and wherein the read-out circuit comprisesa charge-integrating circuit or a transimpedance amplifier.
 15. Thephoton avalanche diode of claim 13, wherein active or passive quenchingis applied to the auxiliary anode terminal, and wherein the read-outcircuit has a digital pulse output.
 16. A method of producing a photonavalanche diode, the method comprising: forming a primary doped regionof a first conductivity type at a first side of a semiconductor body;forming a primary doped region of a second conductivity type oppositethe first conductivity type at a second side of the semiconductor bodyopposite the first side; forming an enhancement region of the secondconductivity type below and adjoining the primary doped region of thefirst conductivity type, the enhancement region forming an activepn-junction with the primary doped region of the first conductivitytype; and forming a collection region of the first conductivity typeinterposed between the enhancement region and the primary doped regionof the second conductivity type, and configured to transport aphotocarrier generated in the collection region or the primary dopedregion of the second conductivity type towards the enhancement region.17. The method of claim 16, wherein the semiconductor body is a Si body,wherein the first conductivity type is n-type, wherein the secondconductivity type is p-type, wherein the primary doped region of thefirst conductivity type is a primary cathode region of the photonavalanche diode, and wherein the primary doped region of the secondconductivity type is a primary anode region of the photon avalanchediode.
 18. The method of claim 16, further comprising: forming anauxiliary doped region of the second conductivity type at the first sideof the semiconductor body and laterally spaced apart from the primarydoped region of the first conductivity type, wherein the auxiliary dopedregion of the second conductivity type is vertically separated from theprimary doped region of the second conductivity type by the collectionregion.
 19. The method of claim 18, further comprising: forming anauxiliary doped region of the first conductivity type at the first sideof the semiconductor body, wherein the auxiliary doped region of thesecond conductivity type is laterally interposed between the auxiliarydoped region of the first conductivity type and the primary doped regionof the first conductivity type at the first side of the semiconductorbody.
 20. The method of claim 18, further comprising: forming columnarregions of the second conductivity type and which vertically extend fromthe primary doped region of the second conductivity type and laterallyconfine the collection region below the enhancement region, wherein theauxiliary doped region of the second conductivity type is electricallyisolated from the columnar regions.
 21. The method of claim 18, furthercomprising: forming a dielectric isolation between the primary dopedregion of the first conductivity type and the auxiliary doped region ofthe second conductivity type at the first side of the semiconductorbody, wherein a doping concentration of the enhancement region decreasesin a region of the enhancement region which is adjacent to where thedielectric isolation meets the primary doped region of the firstconductivity type.
 22. The method of claim 21, wherein forming theauxiliary doped region of the second conductivity type comprises:forming a photoresist on the first side of the semiconductor body, thephotoresist having an opening which partially overlaps with thedielectric isolation so that an inward part of the dielectric isolationremains covered by the photoresist; and implanting dopants of the secondconductivity type into the first side of the semiconductor body throughthe opening in the photoresist.
 23. The method of claim 21, whereinforming the primary doped region of the first conductivity type and theenhancement region comprises: forming a photoresist on the first side ofthe semiconductor body, the photoresist having an opening which has nooverlap with the dielectric isolation so that the photoresist laterallyextends inward beyond an edge of the dielectric isolation; andimplanting dopants of the second conductivity type and dopants of thefirst conductivity type into the first side of the semiconductor bodythrough the opening in the photoresist.